Method of making coated articles having an oxygen barrier coating and coated articles made thereby

ABSTRACT

An article includes a substrate, a functional coating deposited over at least a portion of the substrate, and a protective (barrier) coating deposited over at least a portion of the functional coating. The barrier coating is stable to oxygen-containing gases and limits the transmission of oxygen-containing gases to materials over which it is deposited when subjected to conditioning steps such as heating, bending, and/or tempering.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a continuation-in-part of U.S. applicationSer. No. 10/397,001 filed Mar. 25, 2003, which was acontinuation-in-part of U.S. application Ser. No. 10/133,805 filed Apr.25, 2002, which was a continuation-in-part of U.S. application Ser. No.10/007,382 filed Oct. 22, 2001. This application also claims thebenefits of U.S. Provisional Application Serial No. 60/376,000 filedApr. 25, 2002, all of which applications are herein incorporated byreference in their entirety.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates generally to coated articles having anoxygen barrier coating, e.g., coated automotive transparencies, and tomethods of making the coated articles.

[0004] 2. Description of the Currently Available Technology

[0005] It is known to reduce the heat build-up in the interior of avehicle by providing a laminated windshield having two glass plies withan infrared (IR) or ultraviolet (UV) attenuating solar control coatingpositioned between the plies. The plies protect the solar controlcoating from mechanical and/or chemical damage. These conventionalwindshields are generally made by shaping and annealing two flat glass“blanks” (one of which has the solar control coating deposited thereon)to form two shaped, annealed glass plies and then securing the glassplies together with a plastic interlayer. Because conventional solarcontrol coatings include metal layers that reflect heat, the glassblanks are typically heated and shaped as “doublets”, i.e., the blanksare positioned one on top of another during heating and shaping with thefunctional coating sandwiched between the glass blanks to prevent unevenheating and cooling, which can affect the final shape of the plies.Examples of laminated automotive windshields and methods of making thesame are disclosed in U.S. Pat. Nos. 4,820,902; 5,028,759; and5,653,903.

[0006] The heatability of the doublet is generally limited by theability of the functional coating to withstand the heat treatmentwithout adversely degrading. By “heatability” is meant the maximumtemperature and/or maximum time at a particular temperature to which thecoated substrate can be heated without degradation of the functionalcoating. Such degradation can affect the physical and/or opticalproperties of the coating, such as solar energy reflection and/ortransmission. Such degradation can be caused, for example, by oxidationof various metal-containing layers in the functional coating. Forexample, functional coatings containing metal layers can be sensitive tooxygen in that there can be some change, e.g., decrease, in the opticaland/or solar control properties of the functional coating when thecoated substrate is heat treated, such as by heating, bending,annealing, or tempering, for use in a motor vehicle transparency orwindow or vision panel, or for use in residential or commercial windows,panels, doors, or appliances.

[0007] It would also be advantageous to provide a solar control coatingon other automotive transparencies, such as sidelights, back lights,sunroofs, moon roofs, etc. However, the processes of making laminatedwindshields are not easily adapted to making other types of laminatedand/or non-laminated automotive transparencies. For example,conventional automotive sidelights are usually made from a single glassblank that is individually heated, shaped, and tempered to a desiredcurvature dictated by the dimensions of the vehicle opening into whichthe sidelight is to be installed. A problem posed in making sidelightsnot encountered when making windshields is the problem of individuallyheating glass blanks having a heat-reflecting solar control coating.

[0008] Additionally, if the sidelight is positioned such that thecoating is on the surface of the sidelight facing away from the vehicle(the outer surface), the coating is susceptible to mechanical damagefrom objects hitting the coating and to chemical damage from acid rainor car wash detergents. If the coating is on the surface of thesidelight facing the interior of the vehicle (the inner surface), thecoating is susceptible to mechanical damage from being touched by thevehicle occupants or from being rolled up and down in the windowchannel, and to chemical damage from contact with conventional glasscleaners. Additionally, if the coating is a low emissivity coating itcan promote a greenhouse effect trapping heat inside the vehicle.

[0009] While it is known to reduce chemical damage or corrosion to acoating by overcoating with a chemically resistant material, theseovercoats are typically applied as thin as possible so as not toadversely affect the optical characteristics (e.g., color, reflectance,and transmittance) of the underlying coating and so as not tosignificantly increase the emissivity of the underlying coating. Suchthin overcoats typically do not meet the durability requirements forshipping, processing, or end use of conventional coated automotivetransparencies, which are easily damaged and continuously exposed to theenvironment. Additionally, such thin overcoats would not alleviate thegreenhouse effect problem discussed above. Examples of conventionalovercoats are disclosed in U.S. Pat. Nos. 4,716,086; 4,786,563;5,425,861; 5,344,718; 5,376,455; 5,584,902; and 5,532,180.

[0010] Therefore, it would be advantageous to provide a method of makingan article, e.g., a laminated or non-laminated automotive transparency,or panel, or sheet having a functional coating that reduces oreliminates at least some of the problems discussed above.

SUMMARY OF THE INVENTION

[0011] An article of the invention comprises a substrate, a functionalcoating deposited over at least a portion of the substrate, and aprotective (barrier) coating deposited over at least a portion of thefunctional coating. The functional coating and barrier coating define acoating stack. The barrier coating is stable to oxygen-containing gasesand limits the transmission of oxygen-containing gases to materials overwhich it is deposited when subjected to conditioning processes, such asbut not limited to heating, bending and tempering. The barrier coatingprevents or reduces the diffusion of oxygen or oxygen-containing fluids,e.g., gasses, into the underlying functional coating, especially uponheat treatment of the coated article. The article can be a laminatedarticle comprising two or more substrates. Alternatively, the articlecan be a monolithic article.

[0012] In one particular article, the functional coating can be a solarinfrared reflective coating comprising at least one metaloxide-containing coating film and at least one infrared reflective metalfilm. The protective coating can be formed over at least a portion ofthe functional coating. The protective coating can comprise one or morelayers, e.g., such as a single layer, comprising 0 wt. % to 100 wt. %alumina and/or 100 wt. % to 0 wt. % silica, such as 5 wt. % to 100 wt. %alumina and 95 wt. % to 0 wt. % silica, such as 50 wt. % to 75 wt. %alumina and 50 wt. % to 25 wt. % silica. Alternatively, the protectivecoating can comprise two or more layers, such as a first layercomprising 5 wt. % to 100 wt. % alumina and 95 wt. % to 0 wt. % silica,such as 50 wt. % to 70 wt. % alumina and 50 wt. % to 30 wt. % silica,and a second layer comprising 30 wt. % to 100 wt. % silica and 70 wt. %to 0 wt. % alumina, such as 70 wt. % to 100 wt. % silica and 0 wt. % to30 wt. % alumina. In one non-limiting embodiment, the protective coatingcan have a thickness in the range of 50 Å to 10 microns, such as greaterthan or equal to 100 Å to 10 microns, such as 101 Å to 10 microns, suchas 1 micron to 5 microns. The protective coating can have a refractiveindex in the range of 1 to 3, such as in the range of 1.4 to 2.

[0013] A method of making a conditioned coated substrate comprisesproviding a substrate, forming at least one functional coating over atleast a portion of the substrate, and forming at least one barriercoating over at least a portion of the functional coating to define acoating stack. The barrier coating is stable to oxygen-containing gasesand limits the transmission of oxygen-containing gases to materials overwhich it is deposited. The substrate can be subjected to at least oneconditioning process, such as but not limited to heating, bending,and/or tempering.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a side, sectional view (not to scale) of an edge portionof a laminated automotive transparency, e.g., a sidelight, incorporatingfeatures of the invention;

[0015]FIG. 2 is a perspective, partially broken view of an apparatus(with portions removed for clarity) for producing glass blanks G (coatedor uncoated) in the practice of the invention;

[0016]FIG. 3 is a side, sectional view (not to scale) of a portion of amonolithic article incorporating features of the invention;

[0017]FIG. 4 is a graph showing Taber abrasion test results forsubstrates having a protective coating of the invention compared tosubstrates without the protective coating;

[0018]FIG. 5 is a graph of the average haze for selected substrates ofFIG. 4;

[0019]FIG. 6 is a graph of emissivity value versus coating thickness forsubstrates having a protective coating of the invention;

[0020]FIG. 7 is a graph showing Taber abrasion test results forsubstrates having a protective coating of the invention;

[0021]FIG. 8 is a bar graph showing the effects of heat treatment andcoating thickness on Taber abrasion for coated substrates having aprotective coating of the invention; and

[0022]FIG. 9 is a graph showing the change in the transmittance ofvisible light (Lta) upon heating for a functionally coated substratehaving a protective (barrier) coating of the invention (Line A) and fora functionally coated substrate without the protective (barrier) coating(Line B). The drop-off in slope of Line B indicates a decrease inperformance of the non-protective coated substrate compared to theprotective coated substrate under the same heating conditions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] As used herein, spatial or directional terms, such as “left”,“right”, “inner”, “outer”, “above”, “below”, “top”, “bottom”, and thelike, relate to the invention as it is shown in the drawing figures.However, it is to be understood that the invention may assume variousalternative orientations and, accordingly, such terms are not to beconsidered as limiting. Further, as used herein, all numbers expressingdimensions, physical characteristics, processing parameters, quantitiesof ingredients, reaction conditions, and the like, used in thespecification and claims are to be understood as being modified in allinstances by the term “about”. Accordingly, unless indicated to thecontrary, the numerical values set forth in the following specificationand claims may vary depending upon the desired properties sought to beobtained by the present invention. At the very least, and not as anattempt to limit the application of the doctrine of equivalents to thescope of the claims, each numerical value should at least be construedin light of the number of reported significant digits and by applyingordinary rounding techniques. Moreover, all ranges disclosed herein areto be understood to encompass the beginning and ending range values andany and all subranges subsumed therein. For example, a stated range of“1 to 10” should be considered to include any and all subranges between(and inclusive of) the minimum value of 1 and the maximum value of 10;that is, all subranges beginning with a minimum value of 1 or more andending with a maximum value of 10 or less, e.g., 5.5 to 10. The terms“flat” or “substantially flat” substrate refer to a substrate that issubstantially planar in form; that is, a substrate lying primarily in asingle geometric plane, which substrate, as would be understood by oneskilled in the art, can include slight bends, projections, ordepressions therein. Further, as used herein, the terms “formed over”,“deposited over”, or “provided over” mean formed, deposited, or providedon but not necessarily in contact with the surface. For example, acoating layer “formed over” a substrate does not preclude the presenceof one or more other coating layers or films of the same or differentcomposition located between the formed coating layer and the substrate.For instance, the substrate can include a conventional coating such asthose known in the art for coating substrates, such as glass or ceramic.All documents referred to herein are to be understood to be incorporatedby reference in their entirety. As used herein, the terms “polymer” or“polymeric” refer to oligomers, homopolymers, copolymers, andterpolymers, e.g., polymers formed from two or more types of monomers orpolymers.

[0024] As will be appreciated from the following discussion, theprotective (e.g., barrier) coating of the invention can be utilized inmaking both laminated and non-laminated, e.g., single substrate,articles. As will be appreciated from the following discussion, theprotective or barrier coating of the invention can be utilized in makingboth laminated and non-laminated, e.g., single ply, articles. By“protective coating” or “barrier coating” is meant a film, layer orcoating formed from a protective or barrier material and at a sufficientthickness to limit the transmission of oxygen-containing gases throughthe coating. By “protective material” or “barrier material” is meant amaterial having a low permeability to oxygen-containing gases, such asair or water vapor. The material can exhibit a high resistance to thepassage of oxygen or air or water vapor through the material. Moresuitable barrier material has limited cracking when it is in the form ofa coating at the conditions of the invention and is substantially stableto oxygen at such conditions. As will be appreciated by one skilled inthe coating art, permeation through a material is a function of thethickness of the material. The barrier coating of the present inventionexhibits a combination of relatively high resistance to both air andwater vapor but some applications do not require resistance to both.Therefore, low permeability to either air or water vapor is sufficientto qualify the coating as a “barrier coating.” Embodiments of barriercoatings of the present invention intended primarily as oxygen barrierscan exhibit an oxygen permeability of less than about 1.5, such as lessthan about 1.0, such as less than about 0.5 measured as cubiccentimeters of oxygen gas permeating a one-mil thick sample, 100 inchessquare over a 24-hour period under an oxygen partial pressuredifferential of one atmosphere at 23° C. and at a relative humidity ofzero. The barrier coating can be stable to oxygen containing gasses sothat the coating can withstand conditioning, such as heating to bend,sag, temper, or anneal, with minimal if any change in its oxygen barrierproperties from those that existed before the conditioning step.

[0025] For use with laminated articles, the protective coating canusually be thinner than for non-laminated articles. The structuralcomponents and a method of making an exemplary laminated article of theinvention will first be described and then an exemplary monolithicarticle of the invention will be described. By “monolithic” is meanthaving a single structural support or structural member, e.g., having asingle substrate. In the following discussion, the exemplary article(whether laminated or monolithic) is described as an automotivesidelight. However, the invention is not limited to automotivesidelights but may be used with any articles, such as but not limitedto, insulating glass units, residential or commercial laminated windows(e.g., skylights), or transparencies for land, air, space, above waterand underwater vehicles, e.g. windshields, backlights, sun or moonroofs, just to name a few articles.

[0026]FIG. 1 illustrates a laminated article in the form of a sidelight10 incorporating features of the invention. The laminated sidelight 10includes a first substrate or ply 12 having an outer major surface 13and an inner major surface 14. By “ply” is meant a substrate that hasbeen bent to a desired shape or curvature and/or heat-treated, such asby annealing or tempering. A functional coating 16 can be formed over,e.g., on, at least a portion, preferably all, of the inner major surface14 in any conventional manner, such as but not limited to chemical vapordeposition, magnetron sputter vapor deposition, spray pyrolysis, just toname a few. As will be described in more detail, a barrier or protectivecoating 17 of the invention can be formed over, e.g., on, at least aportion, preferably all, of the functional coating 16 and aids not onlyin increasing mechanical and chemical durability but also providesimproved heating characteristics for bending and/or shaping the blank onwhich it is deposited. A polymeric layer 18 can be located between thefirst ply 12 and a second substrate or ply 20 having an inner majorsurface 22 and an outer major surface 23. In one non-limitingembodiment, the outer major surface 23 can face the exterior of thevehicle and the outer major surface 13 can face the interior of thevehicle. A conventional edge sealant 26 can be applied to the perimeterof the laminated sidelight 10 during and/or after lamination in anyconventional manner. A decorative band 90, e.g., an opaque, translucentor colored band, such as a ceramic band, can be provided on a surface ofat least one of the plies 12 and 20, for example, around the perimeterof one of the inner or outer major surfaces.

[0027] In the broad practice of the invention, the substrates used forfirst ply 12 and second ply 20 can be of any desired material having anydesired characteristics, such as opaque, translucent, or transparent tovisible light. By “transparent” is meant having a transmittance throughthe substrate of greater than 0% up to 100%. By “visible light” or“visible region” is meant electromagnetic energy in the range of 395nanometers (nm) to 800 nm. Alternatively, the substrate can betranslucent or opaque. By “translucent” is meant allowingelectromagnetic energy (e.g., visible light) to pass through thesubstrate but diffusing this energy such that objects on the side of thesubstrate opposite to the viewer are not clearly visible. By “opaque” ismeant having a visible light transmittance of 0%. Examples of suitablesubstrates include, but are not limited to, plastic substrates (such asacrylic polymers, such as polyacrylates; polyalkylmethacrylates, such aspolymethylmethacrylates, polyethylmethacrylates,polypropylmethacrylates, and the like; polyurethanes; polycarbonates;polyalkylterephthalates, such as polyethyleneterephthalate (PET),polypropyleneterephthalates, polybutyleneterephthalates, and the like;polysiloxane containing polymers; or copolymers of any monomers forpreparing these, or any mixtures thereof); metal substrates, such as butnot limited to galvanized steel, stainless steel, and aluminum; ceramicsubstrates; tile substrates; glass substrates; or mixtures orcombinations of any of the above. For example, the substrate can beconventional untinted soda-lime-silica-glass, i.e., “clear glass”, orcan be tinted or otherwise colored glass, borosilicate glass, leadedglass, tempered, untempered, annealed, or heat-strengthened glass. Theglass may be of any type, such as conventional float glass or flatglass, and may be of any composition having any optical properties,e.g., any value of visible radiation transmission, ultraviolet radiationtransmission, infrared radiation transmission, and/or total solar energytransmission. Types of glass suitable for the practice of the inventionare described, for example but not to be considered as limiting, in U.S.Pat. Nos. 4,746,347; 4,792,536; 5,240,886; 5,385,872; and 5,393,593. Theinvention is not limited by the thickness of the substrate. Thesubstrate can generally be thicker for typical architecturalapplications than for typical vehicle applications. In one embodiment,the substrate can be glass having a thickness in the range of 1 mm to 20mm, such as about 1 mm to 10 mm, such as 2 mm to 6 mm, such as 3 mm to 5mm. For forming a laminated automotive sidelight, the first and secondplies 12, 20 can be less than about 3.0 mm thick, such as less thanabout 2.5 mm thick, such as in the thickness range of about 1.0 mm toabout 2.1 mm. As described below, for monolithic articles the substratecan be thicker.

[0028] The substrate can have oxygen barrier properties, e.g., can bemade of a material that prevents or limits the diffusion of oxygenthrough the substrate. Alternatively, another oxygen barrier coating (inaddition to the barrier coating 17 described below) can be formed overat least a portion of the substrate and the functional coating 16 can besubsequently formed over this other oxygen barrier coating. The otheroxygen barrier coating can be of any material to prevent or limit thediffusion of oxygen, such as but not limited to those described belowfor the protective coating 17.

[0029] The functional coating 16 can be of any desired type. As usedherein, the term “functional coating” refers to a coating that modifiesone or more physical properties of the substrate over which it isdeposited, e.g., optical, thermal, chemical or mechanical properties,and is not intended to be entirely removed from the substrate duringsubsequent processing. The functional coating 16 can have one or morefunctional coating layers or films of the same or different compositionor functionality. As used herein, the term “film” refers to a coatingregion of a desired or selected coating composition. A “layer” cancomprise one or more “films” and a “coating” can comprise one or more“layers”.

[0030] For example, the functional coating 16 can be an electricallyconductive coating, such as, for example, an electrically conductivecoating used to make heatable windows as disclosed in U.S. Pat. Nos.5,653,903 and 5,028,759, or a single-film or multi-film coating used asan antenna. Likewise, the functional coating 16 can be a solar controlcoating. As used herein, the term “solar control coating” refers to acoating comprised of one or more layers or films which affect the solarproperties of the coated article, such as but not limited to the amountof solar radiation, for example, visible, infrared, or ultravioletradiation incident on and/or passing through the coated article,infrared or ultraviolet absorption or reflection, shading coefficient,emissivity, etc. The solar control coating can block, absorb or filterselected portions of the solar spectrum, such as but not limited to theIR, UV, and/or visible spectrums. Examples of solar control coatingsthat can be used in the practice of the invention are found, for examplebut not to be considered as limiting, in U.S. Pat. Nos. 4,898,789;5,821,001; 4,716,086; 4,610,771; 4,902,580; 4,716,086; 4,806,220;4,898,790; 4,834,857; 4,948,677; 5,059,295; and 5,028,759, and also inU.S. patent application Ser. No. 09/058,440.

[0031] The functional coating 16 can also be a low emissivity coatingthat allows visible wavelength energy, e.g., 395 nm to 800 nm, to betransmitted through the coating but reflects longer-wavelength solarinfrared energy. By “low emissivity” is meant emissivity less than 0.4,such as less than 0.3, such as less than 0.2, such as less than 0.1,e.g., less than or equal to 0.05. Examples of low emissivity coatingsare found, for example, in U.S. Pat. Nos. 4,952,423 and 4,504,109 andBritish reference GB 2,302,102. The functional coating 16 can be asingle layer coating or multiple layer coating and can include one ormore metals, non-metals, semi-metals, semiconductors, and/or alloys,compounds, composites, combinations, or blends thereof. For example, thefunctional coating 16 can be a single layer metal oxide coating, amultiple layer metal oxide coating, a non-metal oxide coating, ametallic nitride or oxynitride coating, or a non-metallic nitride oroxynitride coating, or a multiple layer coating.

[0032] Examples of suitable functional coatings for use with theinvention are commercially available from PPG Industries, Inc. ofPittsburgh, Pa. under the SUNGATE® and SOLARBAN®) families of coatings.Such functional coatings typically include one or more anti-reflectivecoating films comprising dielectric or anti-reflective materials, suchas metal oxides or oxides of metal alloys, which are transparent tovisible light. The functional coating can also include one or moreinfrared reflective films comprising a reflective metal, e.g., a noblemetal such as gold, copper or silver, or combinations or alloys thereof,and can further comprise a primer film or barrier film, such astitanium, as is known in the art, located over and/or under the metalreflective layer. The functional coating can have any desired number ofinfrared reflective films, such as 1 or more silver layers, e.g., 2 ormore silver layers, e.g., 3 or more silver layers.

[0033] Although not limiting to the invention, the functional coating 16can be positioned on one of the inner major surfaces 14, 22 of thelaminate to make the coating 16 less susceptible to environmental andmechanical wear than if the functional coating 16 were on an outersurface of the laminate. However the functional coating 16 could also beprovided on one or both of the outer major surfaces 13 or 23. As shownin FIG. 1, a portion of the coating 16, e.g., about a 1 mm to 20 mm,such as 2 mm to 4 mm wide area around the outer perimeter of the coatedregion, can be removed or deleted in any conventional manner, e.g., bygrinding prior to lamination or masking during coating, to minimizedamage to the functional coating 16 at the edge of the laminate byweathering or environmental action during use. In addition, deletioncould be done for functional performance, e.g., for antennas, heatedwindshields, or to improve radio-wave transmission, and the deletedportion can be of any size. For aesthetic purposes, a colored, opaque,or translucent band 90 can be provided over any surface of the plies orthe coatings, for example over one or both surfaces of one or both ofthe plies, e.g., around the perimeter of the outer major surface 13, tohide the deleted portion. The band 90 can be made of a ceramic materialand may be fired onto the outer major surface 13 in any conventionalmanner.

[0034] The protective (barrier) coating 17 of the invention can beformed over, e.g., on, at least a portion, preferably all, of the outersurface of the functional coating 16. The protective coating 17, amongother things, can raise the emissivity of the coating stack (e.g., thefunctional coating plus protective coating) to be greater than theemissivity of the functional coating 16 alone. By way of example, if thefunctional coating 16 has an emissivity value of 0.2, the addition ofthe protective coating 17 can raise the emissivity value of theresultant coating stack to an emissivity of greater than 0.2. In oneembodiment, the protective coating can increase the emissivity of theresulting coating stack by a factor of two or more over the emissivityof the functional coating alone (e.g., if the emissivity of thefunctional coating is 0.05, the addition of the protective layer canincrease the emissivity of the resulting coating stack to 0.1 or more),such as by a factor of five or more, e.g., by a factor of ten or more,e.g., by a factor of twenty or more. The protective coating can increasethe emissivity of the at least one functional coating and the at leastone deposited (protective) coating as a stack of coatings when thefunctional coating has an emissivity in the range from 0.02 to 0.30,more suitably 0.03 to 0.15, by a percentage that is from less than 10 to3,000 percent or within this range from 50 to 200 percent or 10 to 200percent or 200 to 1,000 percent or 1,000 to 3,000 percent. In anotherembodiment of the invention, the protective coating 17 can raise theemissivity of the resulting coating stack to be substantially the sameas the emissivity of the substrate on which the coating is deposited,e.g., within 0.2 of the emissivity of the substrate. For example, if thesubstrate is glass having an emissivity of about 0.84, the protectivecoating 17 can provide the coating stack with an emissivity in the rangeof 0.3 to 0.9, such as greater than 0.3, e.g., greater than 0.5, e.g.,greater than 0.6, e.g., in the range of 0.5 to 0.9. As will be describedbelow, increasing the emissivity of the functional coating 16 bydeposition of the protective coating 17 improves the heating and coolingcharacteristics of the coated ply 12 during processing. The protectivecoating 17 also protects the functional coating 16 from mechanical andchemical attack during handling, storage, transport, and processing.

[0035] In one embodiment, the protective coating 17 can have an index ofrefraction (i.e., refractive index) that is substantially the same asthat of the ply 12 to which it is laminated. For example, if the ply 12is glass having an index of refraction of 1.5, the protective coating 17can have an index of refraction of less than 2, such as 1.4 to 1.8, suchas 1.3 to 1.8, e.g., 1.5±0.2.

[0036] The protective coating 17 can be of any desired thickness. In oneexemplary laminated article embodiment, the protective coating 17 canhave a thickness in the range of 100 Å to 50,000 Å, such as 500 Å to50,000 Å, e.g., 500 Å to 10,000 Å, such as 100 Å to 2,000 Å, such as 300Å to 1,500 Å, such as 500 Å to 1,000 Å, such as 800 Å. In othernon-limiting embodiments, the protective coating 17 can have a thicknessin the range of 100 Å to 10 microns, such as 101 Å to 1,000 Å, or 1,000Å to 1 micron, or 1 micron to 10 microns, or 200 Å to 1,000 Å. Further,the protective coating 17 can be of non-uniform thickness across thesurface of the functional coating 17. By “non-uniform thickness” ismeant that the thickness of the protective coating 17 can vary over agiven unit area, e.g., the protective coating 17 can have high and lowspots or areas.

[0037] The protective coating 17 can be of any desired material ormixture of materials. In one exemplary embodiment, the protectivecoating 17 can include one or more metal oxide materials, such as butnot limited to, aluminum oxide, silicon oxide, or mixtures thereof. Forexample, the protective coating can be a single coating layer comprisingin the range of 0 wt. % to 100 wt. % alumina and/or 0 wt. % to 100 wt. %silica, such as 5 wt. % to 100 wt. % alumina and 95 wt. % to 0 wt. %silica, such as 10 wt. % to 90 wt. % alumina and 90 wt. % to 10 wt. %silica, such as 15 wt. % to 90 wt. % alumina and 85 wt. % to 10 wt. %silica, such as 50 wt. % to 75 wt. % alumina and 50 wt. % to 25 wt. %silica, such as 50 wt. % to 60 wt. % alumina and 40 wt. % to 50 wt. %silica, such as 50 wt. % to 70 wt. % alumina and 50 wt. % to 30 wt. %silica, such as 35 wt. % to 100 wt. % alumina and 65 wt. % to 0 wt. %silica, e.g., 70 wt. % to 90 wt. % alumina and 10 wt. % to 30 wt. %silica, e.g., 75 wt. % to 85 wt. % alumina and wt. % to 25 wt. % ofsilica, e.g., 88 wt. % alumina and 12 wt. % silica, e.g., 65 wt. % to 75wt. % alumina and 25 wt. % to 35 wt. % silica, e.g., 70 wt. % aluminaand 30 wt. % silica, e.g., 60 wt. % to less than 75 wt. % alumina andgreater than 25 wt. % to 40 wt. % silica. In one non-limitingembodiment, the protective coating 17 can include 55 wt. % alumina and45 wt. % silica. In one particular non-limiting embodiment, theprotective coating 17 can include 50 wt. % to 60 wt. % alumina, such as55 wt. % alumina and 45 wt. % silica, and can have a thickness in therange of 300 Å to 1,500 Å, such as 500 Å to 1,000 Å, such as 800 Å.Other materials, such as aluminum, chromium, hafnium, yttrium, nickel,boron, phosphorous, titanium, zirconium, and/or oxides thereof, can alsobe present, such as to adjust the refractive index of the coating 17. Inone embodiment, the refractive index of the protective coating can be inthe range of 1 to 3, such as 1 to 2, such as 1.4 to 2, such as 1.4 to1.8.

[0038] Alternatively, the protective coating 17 can be a multilayercoating formed by separately formed layers of metal oxide materials,such as but not limited to a bilayer formed by one metal oxidecontaining layer (e.g., a silica and/or alumina containing first layer)formed over another metal oxide containing layer (e.g., a silica and/oralumina containing second layer). The individual layers of themultilayer protective coating 17 can be of any desired thickness.

[0039] In one embodiment, the protective coating 17 can comprise a firstlayer formed over the functional coating and a second layer formed overthe first layer. In one non-limiting embodiment, the first layer cancomprise alumina or a mixture or alloy comprising alumina and silica.For example, the first layer can comprise alumina or a silica/aluminamixture having greater than 5 wt. % alumina, such as greater than 10 wt.% alumina, such as greater than 15 wt. % alumina, such as greater than30 wt. % alumina, such as greater than 40 wt. % alumina, such as 50 wt.% to 70 wt. % alumina, such as in the range of 70 wt. % to 100 wt. %alumina and 30 wt. % to 0 wt. % silica. In one non-limiting embodiment,the first layer can have a thickness in the range of greater than 0 Å to1 micron, such as 50 Å to 400 Å, such as 50 Å to 200 Å, such as 50 Å to100 Å, such as 100 Å to 250 Å, such as 101 Å to 250 Å, such as 100 Å to150 Å, such as greater than 100 Å to 125 Å.

[0040] The second layer can comprise silica or a mixture or alloycomprising silica and alumina. For example, the second layer cancomprise a silica/alumina mixture having greater than 40 wt. % silica,such as greater than 50 wt. % silica, such as greater than 60 wt. %silica, such as greater than 70 wt. % silica, such as greater than 80wt. % silica, such as in the range of 80 wt. % to 95 wt. % silica and 5wt. % to 20 wt. % alumina, such as in the range of 80 wt. % to 90 wt. %silica and 10 wt. % to 20 wt. % alumina, e.g., 85 wt. % silica and 15wt. % alumina. In one non-limiting embodiment, the second layer can havea thickness in the range of greater than 0 Å to 2 microns, such as 50 Åto 5,000 Å, such as 50 Å to 2,000 Å, such as 100 Å to 1,000 Å, such as300 Å to 1,000 Å, such as 300 Å to 500 Å, such as 350 Å to 400 Å. Asdescribed below, the presence of the protective coating 17 can improvethe heatability of the functionally coated substrate.

[0041] In one particular non-limiting embodiment, the first layer caninclude 100 wt. % alumina and can have a thickness in the range of 50 Åto 200 Å, such as 125 Å. The second layer can include 5 wt. % to 20 wt.% alumina and 80 wt. % to 95 wt. % silica and can have a thickness inthe range of 300 Å to 1,000 Å, such as 500 Å. In another non-limitingembodiment, the first layer can include 50 wt. % to 60 wt. % alumina and40 wt. % to 50 wt. % silica, such as 55 wt. % alumina and 45 wt. %silica, and can have a thickness in the range of 50 Å to 400 Å, such as200 Å. The second layer can include 5 wt. % to 20 wt. % alumina and 80wt. % to 95 wt. % silica and can have a thickness in the range of 300 Åto 1,000 Å, such as 500 Å.

[0042] The polymeric layer 18 can include any polymeric material. The“polymeric material” can comprise one polymeric component or cancomprise a mixture of different polymeric components, such as but notlimited to one or more plastic materials, such as but not limited to oneor more thermoset or thermoplastic materials. The polymeric layer 18 canadhere the plies together. Useful thermoset components includepolyesters, epoxides, phenolics, and polyurethanes such as reactioninjected molding urethane (RIM) thermoset materials and mixturesthereof. Useful thermoplastic materials include thermoplasticpolyolefins such as polyethylene and polypropylene, polyamides such asnylon, thermoplastic polyurethanes, thermoplastic polyesters, acrylicpolymers, vinyl polymers, polycarbonates,acrylonitrile-butadiene-styrene (ABS) copolymers, EPDM rubber,copolymers and mixtures thereof.

[0043] Suitable acrylic polymers include copolymers of one or more ofacrylic acid, methacrylic acid and alkyl esters thereof, such as methylmethacrylate, ethyl methacrylate, hydroxyethyl methacrylate, butylmethacrylate, ethyl acrylate, hydroxyethyl acrylate, butyl acrylate and2-ethylhexyl acrylate. Other suitable acrylics and methods for preparingthe same are disclosed in U.S. Pat. No. 5,196,485.

[0044] Useful polyesters and alkyds can be prepared in a known manner bycondensation of polyhydric alcohols, such as ethylene glycol, propyleneglycol, butylene glycol, 1,6-hexylene glycol, neopentyl glycol,trimethylolpropane and pentaerythritol, with polycarboxylic acids suchas adipic acid, maleic acid, fumaric acid, phthalic acids, trimelliticacid or drying oil fatty acids. Examples of suitable polyester materialsare disclosed in U.S. Pat. Nos. 5,739,213 and 5,811,198.

[0045] Useful polyurethanes include the reaction products of polymericpolyols such as polyester polyols or acrylic polyols with apolyisocyanate, including aromatic diisocyanates such as4,4′-diphenylmethane diisocyanate, aliphatic diisocyanates such as1,6-hexamethylene diisocyanate, and cycloaliphatic diisocyanates such asisophorone diisocyanate and 4,4′-methylene-bis(cyclohexyl isocyanate).The term “polyurethane” as used herein is intended to includepolyurethanes as well as polyureas, and poly(urethane-ureas).

[0046] Suitable epoxy-functional materials are disclosed in U.S. Pat.No. 5,820,987.

[0047] Useful vinyl resins include polyvinyl acetyl, polyvinyl formal,and polyvinyl butyral.

[0048] The polymeric layer 18 can have any desired thickness, e.g., inone non-limiting embodiment for polyvinyl butyral the thickness can bein the range of 0.50 mm to about 0.80 mm, such as 0.76 mm. The polymericmaterial can have any desired refractive index. In one embodiment, thepolymeric material has a refractive index in the range of 1.4 to 1.7,such as 1.5 to 1.6.

[0049] The protective coating 17 can have an index of refraction that issubstantially the same as the refractive index of the polymeric layer 18material. By “substantially the same” refractive index is meant that therefractive index of the protective coating material and the polymericlayer material are the same or sufficiently close that little or noundesirable optical effects, such as undesirable changes in color,reflectance, or transmittance are caused by the presence of theprotective coating 17. In effect, the protective coating 17 behavesoptically as if it were a continuation of the polymeric layer material.The presence of the protective coating 17 preferably does not cause theintroduction of an optically undesirable interface between theprotective coating 17 and the polymeric layer 18. In one embodiment, theprotective coating 17 and polymeric layer 18 can have indices ofrefraction that are within ±0.2 of each other, such as within ±0.1, suchas within ±0.05. By providing that the refractive index of theprotective coating material is the same as or substantially the same asthe refractive index of the polymeric layer material, the presence ofthe protective coating 17 does not adversely impact upon the opticalproperties of the laminated article compared to the optical propertiesof the laminated article without the protective coating 17. For example,if the polymeric layer 18 comprises polyvinyl butyral having an index ofrefraction of 1.5, the protective coating 17 can be selected or formedto have an index of refraction of less than 2, such as 1.3 to 1.8, e.g.,1.5±0.2.

[0050] An exemplary method of making a laminated sidelight 10 utilizingfeatures of the invention will now be discussed.

[0051] A first substrate and a second substrate are provided. The firstand second substrates can be flat glass blanks having a thickness ofabout 1.0 mm to 6.0 mm, typically about 1.0 mm to about 3.0 mm, such asabout 1.5 mm to about 2.3 mm. A functional coating 16 can be formed overat least a portion of a major surface of the first glass substrate, forexample, the major surface 14. The functional coating 16 can be formedin any conventional manner, such as but not limited to, magnetronsputter vapor deposition (MSVD), pyrolytic deposition such as chemicalvapor deposition (CVD), spray pyrolysis, atmospheric pressure CVD(APCVD), low-pressure CVD (LPCVD), plasma-enhanced CVD (PEVCD), plasmaassisted CVD (PACVD), or thermal evaporation by resistive orelectron-beam heating, cathodic arc deposition, plasma spray deposition,wet chemical deposition (e.g., sol-gel, mirror silvering, etc.), or anyother desired manner. For example, the functional coating 16 can beformed over the first substrate after the first substrate is cut to adesired dimension. Alternatively, the functional coating 16 can beformed over a glass sheet before it is processed and/or over a floatglass ribbon supported on a bath of molten metal, e.g., tin, in aconventional float chamber by one or more conventional CVD coaterspositioned in the float chamber. Upon exiting the float chamber, theribbon can be cut to form the coated first substrate.

[0052] Alternatively, the functional coating 16 can be formed over thefloat glass ribbon after the ribbon exits the float chamber. Forexample, U.S. Pat. Nos. 4,584,206, 4,900,110, and 5,714,199 disclosemethods and apparatus for depositing a metal-containing film on thebottom surface of a glass ribbon. Such a known apparatus can be locateddownstream of a molten tin bath in the float glass process to provide afunctional coating on the bottom of the glass ribbon, i.e., the side ofthe ribbon that was in contact with the molten metal. Still further, thefunctional coating 16 can be formed over the first substrate by MSVDafter the substrate has been cut to a desired dimension.

[0053] A protective coating 17 of the invention can be formed over atleast a portion of the functional coating 16. The protective coating 17provides several processing advantages in making the laminated article.For example, the protective coating 17 can protect the functionalcoating 16 from mechanical and/or chemical attack during handling,transport, storage, and processing. Additionally, as described below,the protective coating 17 can facilitate individual heating and coolingof the functionally coated blank by increasing the emissivity of theresulting coating stack. While topcoats have been applied ontofunctional coatings in the past to help protect the functional coatingfrom chemical and mechanical attack during processing, these topcoatswere made as thin as possible so as not to impact upon the aesthetic orsolar control properties of the functional coating, such as the coatingemissivity. Conversely, in the present invention, the protective coating17 can be made sufficiently thick so as to raise the emissivity of thecoating stack. Further, by substantially matching the index ofrefraction of the protective coating 17 to that of the polymeric layer18 material (and/or the substrate to which it is laminated), there islittle or no adverse impact by the presence of the protective coating 17upon the aesthetic and/or optical characteristics of the laminatedarticle 10.

[0054] If the functional coating 16 is a low emissivity coating havingone or more infrared reflecting metal layers, the addition of theprotective coating 17 to raise the emissivity of the coating stackreduces the thermal infrared reflecting characteristics of thefunctional coating 16. However, the coating stack remains solar infraredreflective.

[0055] The protective coating 17 can be formed in any conventionalmanner, such as but not limited to those described above for applyingthe functional coating, e.g., in-bath or out-of-bath CVD, MSVD; orsol-gel, just to name a few. For example, the substrate with thefunctional coating can be directed to a conventional MSVD coatingapparatus having one or more metal electrodes, e.g., cathodes, that canbe sputtered in an oxygen-containing atmosphere to form a metal oxideprotective coating. In one non-limiting embodiment, the MSVD apparatuscan include one or more cathodes of aluminum, silicon, or mixtures oralloys of aluminum or silicon. The cathodes can be for example, 5 wt. %to 100 wt. % aluminum and 95 wt. % to 0 wt. % silicon, such as 10 wt. %to 100 wt. % aluminum and 90 wt. % to 0 wt. % silicon, such as 35 wt. %to 100 wt. % aluminum and 0 wt. % to 65 wt. % silicon, e.g., 50 wt. % to80 wt. % aluminum and 20 wt. % to 50 wt. % silicon, e.g., 70 wt. %aluminum and 30 wt. % silicon. Additionally, other materials or dopants,such as aluminum, chromium, hafnium, yttrium, nickel, boron,phosphorous, titanium, or zirconium, can also be present to facilitatesputtering of the cathode(s) and/or to affect the refractive index ordurability of the resultant coating. As described above, the protectivecoating 17 can be formed as a single layer comprising one or more metaloxide materials or as a multilayer coating having two or more separatelayers, with each separate layer comprising one or more metal oxidematerials. The protective coating 17 can be applied in a sufficientamount or to a sufficient thickness to raise the emissivity of thecoating stack over that of just the functional coating alone. In oneembodiment, the protective coating can be applied to a thickness in therange of 100 Å to 50,000 Å and/or to raise the emissivity of the coatingstack to greater than or equal to about 0.3, e.g., greater than or equalto 0.4, e.g., greater than or equal to 0.5.

[0056] The functional coating 16 and/or protective coating 17 can beapplied to the flat substrate or to the substrate after the substratehas been bent and shaped to a desired contour.

[0057] The coated first substrate and uncoated second substrate can becut to provide a first, coated ply and a second, uncoated ply,respectively, each having a desired shape and desired dimensions. Thecoated and uncoated plies can be seamed, washed, bent, and shaped to adesired contour to form the first and second plies 12 and 20,respectively, to be laminated. As can be appreciated by one of ordinaryskill in the art, the overall shapes of the coated and uncoated blanksand plies depend upon the particular vehicle into which they will beincorporated, since the final shape of a sidelight differs betweendifferent automotive manufacturers.

[0058] The coated and uncoated blanks can be shaped using any desiredprocess. For example, the blanks can be shaped using the “RPR” processdisclosed in U.S. Pat. No. 5,286,271 or the modified RPR processdisclosed in U.S. patent application Ser. No. 09/512,852. FIG. 2 showsan additional RPR apparatus 30 suitable for the practice of theinvention and includes a furnace 32, e.g., a radiant heat furnace ortunnel Lehr, having a furnace conveyor 34 comprised of a plurality ofspaced furnace conveyor rolls 36. Heaters, such as radiant heater coils,can be positioned above and/or below the furnace conveyor 34 along thelength of the furnace 32 and can be controlled to form heating zones ofdifferent temperature along the length of the furnace 32.

[0059] A shaping station 50 can be located adjacent the discharge end ofthe furnace 32 and can include a lower mold 51 having a verticallymovable flexible ring 52 and a shaping station conveyor 54 having aplurality of rolls 56. An upper vacuum mold 58 having a removable orreconfigurable shaping surface 60 of a predetermined shape can belocated above the lower mold 51. The vacuum mold 58 can be movable via ashuttle arrangement 61.

[0060] A transfer station 62 having a plurality of shaped transfer rolls64 can be located adjacent a discharge end of the shaping station 50.The transfer rolls 64 can have a transverse elevational curvaturecorresponding substantially to the transverse curvature of the shapingsurface 60.

[0061] A tempering or cooling station 70 can be located adjacent adischarge end of the transfer station 62 and can include a plurality ofrolls 72 to move the blanks through the station 70 for cooling,tempering, and/or heat strengthening. The rolls 72 can have a transverseelevational curvature substantially the same as that of the transferrolls 64.

[0062] In the past, heating functionally coated blanks (substrates)presented difficulties due to the heat reflectance of the functionalcoating 16, which caused uneven heating of the coated and uncoated sidesof the blank. U.S. patent application Ser. No. 09/512,852 discloses amethod of overcoming this problem by modifying the RPR heating processto supply heat primarily toward the non-functionally coated surface ofthe blank. In the present invention, this problem is addressed bydeposition of the emissivity increasing protective coating 17, whichallows the same or substantially the same heating process to be usedboth for the functionally coated and non-functionally coated blanks.

[0063] As shown in FIG. 2, the first blank 80 with the coating stack(e.g., functional coating 16 and protective coating 17) and thenon-functionally coated second blank 82 can be individually heated,shaped, and cooled prior to lamination. By “individually heated” ismeant that the blanks are not stacked one on top of the other duringheating. In one embodiment, the first blank 80 is placed on the furnaceconveyor 34 with the protective coating 17 facing downwardly, i.e., incontact with the furnace conveyor rolls 36, during the heating process.The presence of the higher emissivity protective coating 17 reduces theproblem of heat reflectance by the metal layers of the functionalcoating 16 and promotes more even heating of the coated and uncoatedsides of the first blank 80. This helps prevent curling of the firstblank 80 common in prior heating processes. In one exemplary embodiment,the blanks are heated to a temperature of about 640° C. to 704° C.during a period of about 10 mins to 30 mins.

[0064] At the end of the furnace 32, the softened glass blanks, whethercoated 80 or non-coated 82, are moved from the furnace 32 to the shapingstation 50 and onto the lower mold 51. The lower mold 51 moves upwardly,lifting the glass blank to press the heat-softened glass blank againstthe shaping surface 60 of the upper mold 58 to conform the glass blankto the shape, e.g., curvature, of the shaping surface 60. The uppersurface of the glass blank is in contact with the shaping surface 60 ofthe upper mold 58 and is held in place by vacuum.

[0065] The shuttle arrangement 61 is actuated to move the upper vacuummold 58 from the shaping station 50 to the transfer station 62, wherethe vacuum is discontinued to release the shaped glass blank onto thecurved transfer rolls 64. The transfer rolls 64 move the shaped glassblank onto the rolls 72 and into the cooling station 70 for tempering orheat strengthening in any convenient manner. In the cooling station 70,air is directed from above and below the shaped glass blanks to temperor heat strengthen the glass blanks to form the first and second plies12 and 20. The presence of the high emissivity protective coating 17also promotes more even cooling of the coated blank 80 in the coolingstation 70.

[0066] In another embodiment, the coated and uncoated blanks can beheated and/or shaped as doublets. In one embodiment, the coated anduncoated blanks can be positioned such that the functional coating 16with the protective coating 17 is located between the two blanks. Theblanks can then be heated and/or shaped in any conventional manner. Itis believed that the protective coating 17 acts as an oxygen barrier toreduce or prevent oxygen passing into the functional coating 16 wherethe oxygen could react with components of the functional coating 16,such as but not limited to metals (e.g., silver), to degrade thefunctional coating 16. In one conventional method, the doublet can beplaced on a support and heated to sufficient temperature to bend orshape the blanks to a desired final contour. In the absence of theprotective coating 17, typical functionally coated blanks cannotwithstand a heating cycle having heating above about 1100° F. (593° C.)for more than about two minutes (with heating above 900° F. (482° C.)for more than about six minutes during the heating cycle) withoutdegradation of the functional coating 16. Such degradation can take theform of a hazy or yellowish appearance with a decrease in visible lighttransmission of 10% or more. Metal layers in the functional coating 16,such as silver layers, can react with oxygen diffusing into thefunctional coating 16 or with oxygen present in the functional coating16. However, it is believed that utilizing the protective coating 17will permit the functionally coated blank to withstand a heating cyclewith heating to a temperature of 1100° F. (593° C.) or more for a periodof five to fifteen minutes, such as five to ten minutes, such as five tosix minutes (with heating above 900° F. (482° C.) for ten to twentyminutes, such as ten to fifteen minutes, such as ten to twelve minutesduring the heating cycle), with no significant degradation of thefunctional coating 16, e.g., with less than 5% loss of visible lighttransmission, such as less than 3% loss, such as less than 2% loss, suchas less than 1% loss, such as no loss of visible light transmission.

[0067] To form the laminated article 10 of the invention, the coatedglass ply 12 is positioned with the coated inner major surface 14 facingthe substantially complimentary inner major surface 22 of the non-coatedply 20 and separated therefrom by the polymeric layer 18. A portion,e.g. a band of about 2 mm in width, of the coating 16 and/or protectivecoating 17 can be removed from around the perimeter of the first ply 12before lamination. The ceramic band 90 can be provided on one or both ofthe plies 12 or 20, e.g., on the outer surface 13 of the first ply 12,to hide the non-coated peripheral edge region of the laminated sidelightand/or to provide additional shading to passengers inside the vehicle.The first ply 12, polymeric layer 18 and second ply 20 can be laminatedtogether in any convenient manner, for example but not to be consideredas limiting, as disclosed in U.S. Pat. Nos. 3,281,296; 3,769,133; and5,250,146 to form the laminated sidelight 10 of the invention. An edgesealant 26 can be applied to the edge of the sidelight 10, as shown inFIG. 1.

[0068] Although the above method of forming the laminated sidelight 10of the invention utilizes an RPR apparatus and method, the sidelight 10of the instant invention may be formed with other methods, such ashorizontal press bending methods disclosed, for example, in U.S. Pat.Nos. 4,661,139; 4,197,108; 4,272,274; 4,265,650; 4,508,556; 4,830,650;3,459,526; 3,476,540; 3,527,589; and 4,579,577.

[0069]FIG. 3 illustrates a monolithic article 100, in particular amonolithic automotive transparency, incorporating features of theinvention. The article 100 includes a substrate or ply 102 having afirst major surface 104 and a second major surface 106. A functionalcoating 108 can be formed over at least a portion, such as the majority,e.g., all, of the surface area of the first major surface 104. Aprotective coating 110 of the invention can be formed over at least aportion, such as the majority, e.g., all, of the surface area of thefunctional coating 108. The functional coating 108 and protectivecoating 110 can be formed in any desired method, such as those describedabove. The functional coating 108 and protective coating 110 define acoating stack 112. The coating stack 112 can include other coatinglayers or films, such as but not limited to a conventional colorsuppression layer or a sodium ion diffusion barrier layer, just to namea few. An optional polymeric layer 113, such as comprising one or morepolymeric materials such as those described above, can be deposited overthe protective coating 110 in any desired manner.

[0070] The ply 102 can be of any desired material, such as thosedescribed above for the plies 12, 20 and can be of any desiredthickness. In one non-limiting embodiment for use as a monolithicautomotive sidelight, the ply 102 can have a thickness of less than orequal to 20 mm, e.g., less than about 10 mm, such as about 2 mm to about8 mm, e.g., about 2.6 mm to about 6 mm.

[0071] The functional coating 108 can be of any desired type orthickness, such as those described above for the functional coating 16.In one embodiment, the functional coating 108 is a solar control coatinghaving a thickness of about 600 Å to about 2400 Å.

[0072] The protective coating 110 can be of any desired material andhave any desired structure, such as those described above for theprotective coating 17. The protective coating 110 of the invention canbe formed in an amount sufficient to increase, e.g., significantlyincrease, the emissivity of the coating stack 112 over the emissivity ofjust the functional coating 108 alone. For one exemplary monolithicarticle, the protective coating 110 can have a thickness of greater thanor equal to 1 micron, such as in the range of 1 micron to 5 microns. Inone embodiment, the protective coating 110 increases the emissivity ofthe coating stack 112 by at least a factor of 2 over the emissivity ofthe functional coating 108 alone (i.e., if the emissivity of thefunctional coating 108 is 0.05, the addition of the protective coating110 increases the emissivity of the resultant coating stack 112 to atleast 0.1). In another embodiment, the protective coating 110 increasesthe emissivity by at least a factor of 5, such as by a factor of 10 ormore. In a further embodiment, the protective coating 110 increases theemissivity of the coating stack 112 to 0.5 or more, such as greater than0.6, e.g., in the range of about 0.5 to about 0.8.

[0073] Increasing the emissivity of the coating stack 112 maintains thesolar energy reflectance of the functional coating 108 (e.g.,reflectance of electromagnetic energy in the range of 700 nm to 2100 nm)but decreases the thermal energy reflecting capability of the functionalcoating 108 (e.g., reflectance of electromagnetic energy in the range of5000 nm to 25,000 nm). Increasing the emissivity of the functionalcoating 108 by formation of the protective coating 110 also improves theheating and cooling characteristics of the coated substrate duringprocessing, as described above in discussing the laminated article. Theprotective coating 110 also protects the functional coating 108 frommechanical and chemical attack during handling, storage, transport, andprocessing.

[0074] The protective coating 110 can have an index of refraction thatis the same or substantially the same as that of the ply 102 over whichit is deposited. For example, if the ply 102 is glass having an index ofrefraction of 1.5, the protective coating 110 can have an index ofrefraction of less than 2, such as 1.3 to 1.8, such as 1.4 to 1.8, e.g.,1.5±0.2. Additionally or alternatively, the protective coating 110 canhave a refractive index that is substantially the same as the refractiveindex of the polymeric layer 113.

[0075] The protective coating 110 can be of any thickness. In onemonolithic embodiment, the protective coating 110 can have a thicknessof 1 micron or more to reduce or prevent a color variation in theappearance of the article 100. The protective coating 110 can have athickness less than 5 microns, such as in the range of 1 to 3 microns.In one embodiment, the protective coating 110 can be sufficiently thickto pass the conventional ANSI/SAE 26.1-1996 test with less than 2% glossloss over 1000 revolutions in order to be used as an automotivetransparency. The protective coating 110 need not be of uniformthickness across the surface of the functional coating 108 but may havehigh and low spots or areas.

[0076] The protective coating 110 can be a single layer comprising oneor more metal oxide materials, such as those described above.Alternatively, the protective coating 110 can be a multilayer coatinghaving two or more coating layers, such as described above. Each coatinglayer can comprise one or more metal oxide materials. For example, inone embodiment, the protective coating 110 can comprise a first layercomprising aluminum oxide and a second layer comprising silicon oxide.The individual coating layers can be of any desired thickness, such asdescribed above.

[0077] The substrate with the coating stack 112 can be heated and/orshaped in any desired manner, such as that described above for heatingthe coated blank of the laminated article.

[0078] The optional polymeric layer 113 can include one or morepolymeric components, such as those described above for polymeric layer18. The polymeric layer 113 can be of any desired thickness. In onenon-limiting embodiment, the polymeric layer 113 can have a thicknessgreater than 100 Å, such as greater than 500 Å, such as greater than1000 Å, such as greater than 1 mm, such as greater than 10 mm, such asin the range of 100 Å to 10 mm. The polymeric layer 113 can be apermanent layer (i.e., not intended to be removed) or can be a temporarylayer. By “temporary layer” is meant a layer intended to be removed,such as but not limited to removal by combustion or washing with asolvent, in a subsequent processing step. The polymeric layer 113 can beformed by any conventional method.

[0079] The monolithic article 100 is particularly useful as anautomotive transparency. As used herein, the term “automotivetransparency” refers to an automotive sidelight, back light, moon roof,sunroof, and the like. The “transparency” can have a visible lighttransmission of any desired amount, e.g., 0% to 100%. For vision areas,the visible light transmission is preferably greater than 70%. Fornon-vision areas, the visible light transmission can be less than 70%.

[0080] If the ply 102 with only the functional coating 108 were used asan automotive transparency, such as a sidelight, the low emissivityfunctional coating 108 could reduce solar energy passing into theautomobile but could also promote a greenhouse effect trapping thermalenergy inside the automobile. The protective coating 110 of theinvention overcomes this problem by providing a coating stack 112 havinga low emissivity functional coating 108 (e.g., emissivity of 0.1 orless) on one side of the coating stack 112 and a high emissivityprotective coating 110 (e.g., emissivity of 0.5 or more) on the otherside. The solar reflecting metal layers in the functional coating 108reduce solar energy passing into the interior of the automobile and thehigh emissivity protective coating 110 reduces the greenhouse effect andpermits thermal energy inside the automobile to be removed.Additionally, layer 110 (or layer 17) can be solar absorbing in one ormore of the UV, IR, and/or visible regions of the electromagneticspectrum.

[0081] With respect to FIG. 3, the article 100 can be placed in anautomobile with the protective coating 110 facing a first side 114 ofthe automobile and the ply 102 facing a second side 116 of theautomobile. If the first side 114 faces the exterior of the vehicle, thecoating stack 112 will reflect solar energy due to the reflective layerspresent in the functional coating 108. However, due to the highemissivity, e.g., greater than 0.5, of the coating stack 112, at leastsome of the thermal energy will be absorbed. The higher the emissivityof the coating stack 112, the more thermal energy will be absorbed. Theprotective coating 110, in addition to providing increased emissivity tothe coating stack 112, also protects the less durable functional coating108 from mechanical and chemical damage. The optional polymeric layer113 can also provide mechanical and/or chemical durability.

[0082] Alternatively, if the first side 114 faces the interior of thevehicle, the article 100 still provides solar reflectance due to themetal layers in the functional coating 108. However, the presence of theprotective coating 110 reduces thermal energy reflectance by absorbingthe thermal energy to prevent the thermal energy from heating the carinterior to elevate its temperature and reduces the greenhouse effect.Thermal energy from the interior of the vehicle is absorbed by theprotective coating 110 and is not reflected back into the interior ofthe vehicle.

[0083] Although particularly useful for automotive transparencies, thecoating stack of the invention should not be considered as limited toautomotive applications. For example, the coating stack can beincorporated into a conventional insulating glass (IG) unit, e.g., canbe provided on a surface, either inner or outer surface, of one of theglass sheets forming the IG unit. If on an inner surface in the airspace, the coating stack would not have to be as mechanically and/orchemically durable as it would if on an outer surface. Additionally, thecoating stack could be used in a seasonably adjustable window, such asdisclosed in U.S. Pat. No. 4,081,934. If on an outer surface of thewindow, the protective coating should be sufficiently thick to protectthe functional coating from mechanical and/or chemical damage. Theinvention could also be used as a monolithic window.

[0084] Illustrating the invention are the following examples which,however, are not to be considered as limiting the invention to theirdetails. All parts and percentages in the following examples, as well asthroughout the specification are by weight unless otherwise indicated.

EXAMPLE 1

[0085] Several Samples of functional coatings with different protectivecoatings of the invention were prepared and tested for durability,scattered light haze developed after Taber abrasion, and emissivity. Thefunctional coatings were not optimized for mechanical or opticalproperties but were utilized simply to illustrate the relativeproperties, e.g., durability, emissivity, and/or haze, of afunctionally-coated substrate having a protective coating of theinvention. Methods of preparing such functional coatings are described,for example but not to be considered as limiting, in U.S. Pat. Nos.4,898,789 and 6,010,602.

[0086] Test samples were produced by overcoating different functionalcoatings as described below (on common soda lime clear glass) withaluminum oxide protective coatings incorporating features of theinvention and having thickness in the range of 300 Å to 1.5 microns. Thefunctional coatings used in the tests have high solar infraredreflectance and characteristic low emissivity and are comprised ofmultilayer interference thin films achieved by depositing alternatinglayers of zinc stannate and silver by magnetron sputtering vacuumdeposition (MSVD). For the samples discussed below, typically two silverlayers and three zinc stannate layers were present in the functionalcoating. Thin titanium metal primer layers are also used in thefunctional coatings on top of the silver layers to protect the silverlayers from oxidation during MSVD deposition of the oxide zinc stannatelayers and to survive heating to bend the glass substrate. The twofunctional coatings used in the following examples differ mainly in theoutermost thin layer of the multilayer coating, one being metallic Tiand the other being oxide TiO2. Thickness of either the Ti or TiO₂ outerlayer is in the range 10 Å to 100 Å. Alternative examples which areequally applicable but which were not prepared are functional coatingswithout a Ti or TiO2 outer layer or different metallic or oxide outerlayers. The functional coatings used for the examples having the thin Tiouter layer have a blue reflecting color after heating and with the TiO₂outer layer have a green reflecting color after heating. Other resultingreflecting colors of functional coatings after heating which can beprotected with a protective coating of the invention can be achieved bychanging the thickness of the individual silver and zinc stannate layersin the functional coating.

[0087] Thin or thick aluminum oxide protective coatings for thefollowing examples were deposited by mid-frequency, bi-polar, pulseddual magnetron reactive sputtering of Al in an Airco ILS 1600, speciallymodified to power two of the three targets. Power was provided by anAdvanced Energy(AE) Pinnacle® Dual DC power supply and Astral® switchingaccessory, that converts the DC supply to a bi-polar, pulsed supply.Glass substrates with the functional coating were introduced into theAirco ILS 1600 MSVD coater having an oxygen reactive oxygen/argonatmosphere. Two aluminum cathodes were sputtered for different times toachieve the different thickness aluminum oxide coatings over thefunctional coatings.

[0088] Three sample coupons (Samples A-C) were prepared and evaluated asfollows:

[0089] Sample A—4 inch by 4 inch (10 cm by 10 cm) pieces of 2 mm thickclear float glass commercially available from PPG Industries, Inc., ofPittsburgh, Pa.

[0090] Sample B—4 inch by 4 inch (10 cm by 10 cm) pieces of 2 mm thickclear glass coupons having an experimental low emissivity functionalcoating approximately 1600 Å thick with green reflecting color producedby MSVD (as described above) and no protective aluminum oxide protectivecoating were used as a control sample.

[0091] Sample C—4 inch by 4 inch (10 cm by 10 cm) pieces of 2 mm thickglass coupons having an experimental functional coating approximately1600 Å thick with blue reflecting color produced by MSVD but furtherhaving a 1.53 micron thick aluminum oxide (Al₂O₃) protective coating ofthe invention deposited over the functional coating.

[0092] Replicate Samples A-C were then tested in accordance with astandard Taber Abrasion Test (ANSI/SAE 26.1-1996) and the results areshown in FIG. 4. Scratch density (SD) measurements after Taber for agiven number of cycles were determined by microscope measurements of thetotal scratch length of all scratches in a square micron area usingdigitizing and image analysis software. The Sample C (protective coated)coupons showed a lower scratch density than the Sample B (functionallycoated) coupons. The Sample C coupons had about the same durability asthe uncoated glass coupons of Sample A. The Taber results were obtainedfor the “as deposited” protective coating, meaning the coated glasscoupons were not post-heated after MSVD deposition of the protectivecoating. It is expected that the scratch density results should improve(i.e., the scratch density for few Taber cycles should decrease) uponheating of the coated substrate due to increased density of the heatedcoating stack. For example, the coated substrates could be heated fromambient to a maximum temperature in the range of 640° C. to 704° C. andcooled over a time period of about 10 mins to about 30 mins.

[0093]FIG. 5 shows the average scattered light haze versus Taber cycles(in accordance with ANSI/SAE 26.1-1996) for replicate Samples A and C asdescribed above. Sample A is uncoated glass used as a control. Resultsindicate that the haze that develops for Sample C after 1000 cycles isclose to 2%, the minimum acceptable specified by ANSI for automotiveglazing safety. A modest improvement in the durability of the protectivecoating is expected to result in less than 2% haze after 1000 Tabercycles, exceeding the ANSI safety specification for automotive glazing.

[0094]FIG. 6 shows the effect of a protective overcoat of the inventiondeposited at different MSVD process vacuum pressures over two differentfunctional coatings. The Samples shown in FIG. 6 are 2 mm thick couponsof clear float glass with the following coatings deposited thereon:

[0095] Sample D—control sample; nominally 1600 Å thick blue reflectingfunctional coating having no protective coating.

[0096] Sample E—control sample; nominally 1600A thick green reflectingfunctional coating having no protective coating.

[0097] Sample F(HP)—the functional coating of Sample D plus an aluminumoxide protective coating sputter deposited as described above at an MSVDprocess vacuum pressure of 8 microns of oxygen and argon.

[0098] Sample F(LP)—the functional coating of Sample D plus an aluminumoxide protective coating sputter deposited as described above at an MSVDprocess vacuum pressure of 4 microns of oxygen and argon.

[0099] Sample G(HP)—the functional coating of Sample E plus an aluminumoxide protective coating sputter deposited as described above at an MSVDprocess vacuum pressure of 8 microns of oxygen and argon.

[0100] Sample G(LP)—the functional coating of Sample E plus an aluminumoxide protective coating sputter deposited as described above at an MSVDprocess vacuum pressure of 4 microns of oxygen and argon.

[0101] As shown in FIG. 6, as the thickness of the protective coatingincreases, the emissivity of coating stack also increases. At aprotective coating thickness of about 1.5 microns, the coating stack hadan emissivity of greater than about 0.5.

[0102]FIG. 7 shows the results of scratch density measurements after 10cycles Taber abrasion for Samples F(HP), F(LP), G(HP), and G(LP)described above. The control functional Samples D and E with noprotective coating had initial scratch densities on the order of about45 mm⁻¹ to 50 mm⁻¹. As shown in FIG. 7, the application of a protectivecoating of the invention (even on the order of less than about 800 Å)improves the durability of the resultant coating stack.

[0103]FIG. 8 shows the results of scratch density measurements after 10cycles Taber abrasion for the following Samples of blue or greenreflecting functional coatings with aluminum oxide protective coatings300 Å, 500 Å, and 700 Å thick:

[0104] Sample H—the functional coating of Sample D plus an aluminumoxide protective coating sputter deposited as described above by MSVD.

[0105] Sample I—the functional coating of Sample E plus an aluminumoxide protective coating sputter deposited as described above by MSVD.

[0106] As shown on the right side of FIG. 8, heating the coating stackof the invention improves the durability of the coating stack. Thecoatings on the right side of FIG. 8 were heated by insertion in a 1300°F. oven for 3 mins, and then removed and placed in a 400° F. oven for 5mins, after which the coated samples were removed and allowed to coolunder ambient conditions.

EXAMPLE 2

[0107] This Example illustrates the effect of the protective coating ofthe invention on the visible light transmittance of a coated substrateupon heating.

[0108] A glass piece (Sample J) was prepared having a conventionalinfrared reflecting solar control coating without a protective coatingof the invention and another glass piece (Sample K) was prepared havingthe same infrared reflecting solar control coating but with a protectivecoating of the invention. The protective coating in this example was amixture of silica and alumina (70 wt. % alumina and 30 wt. % silica at athickness of 600 Å to 700 Å). The two samples were heated in aconventional oven and the percent of visible light transmittance (Lta)of the two samples was measured at different heating percents. The“heating percent” values in FIG. 9 represent the thermal budget of theheated substrates based on a reference value (0%). By “thermal budget”is meant the highest temperature achieved and the overall time ofheating. The higher the heating percent, the hotter the samples wereheated. As will be seen from Line B in FIG. 9, as the non-protectivecoated Sample J is heated above the reference value, the visible lighttransmittance decreases and drops below 75 percent at a heating percentof about 20%. As will be appreciated by one skilled in the automotiveart, visible light transmittance below about 75 percent is undesirablefor most windshield application. However, as also seen in FIG. 9, theprotective coated Sample K under the same heating conditions maintainsvisible light transmittance above 75 percent even at 40 heating percent(Line A). Thus, the protective coating of the invention permits afunctionally coated substrate to be heated to higher temperatures and/orfor longer periods of time without adversely impacting upon visiblelight transmittance. This feature would be advantageous for operationssuch as deep sag bending or similar operations in which prolongedheating is desired.

[0109] It will be readily appreciated by those skilled in the art thatmodifications may be made to the invention without departing from theconcepts disclosed in the foregoing description. For example, althoughin the preferred embodiment of the laminated article only one plyincludes a functional coating, it is to be understood that the inventioncould also be practiced with both plies having a functional coating orone ply having a functional coating and the other ply having anon-functional coating, e.g., a photocatalytic coating. Moreover, aswill be appreciated by one of ordinary skill in the art, the preferredoperating parameters described above can be adjusted, if required, fordifferent substrate materials and/or thicknesses. Accordingly, theparticular embodiments described in detail herein are illustrative onlyand are not limiting to the scope of the invention, which is to be giventhe full breadth of the appended claims and any and all equivalentsthereof.

What is claimed is:
 1. An article, comprising: a substrate; a functionalcoating deposited over at least a portion of the substrate; and abarrier coating deposited over at least a portion of the functionalcoating to define a coating stack, wherein the barrier coating is stableto oxygen-containing gases and limits the transmission ofoxygen-containing gases to materials over which it is deposited whensubjected to conditioning comprising one or more of heating, bending,and tempering.
 2. The article of claim 1, wherein the substrate is anoxygen barrier.
 3. The article of claim 1, wherein the substrateincludes at least one other barrier coating formed over at least aportion of the substrate and wherein the functional coating is formedover the at least one other barrier coating.
 4. The article of claim 1,wherein the barrier coating has a thickness in the range of greater than100 Å to less than 10 microns.
 5. The article of claim 1, wherein thebarrier coating has a refractive index in the range of 1.4 to 1.8. 6.The article of claim 1, wherein the substrate is selected from glass,plastic, and ceramic.
 7. The article of claim 1, wherein the article isan automotive transparency.
 8. The article of claim 1, wherein thearticle is selected from the group of comprising a window, a single paneof glass, a window with multiple panes of glass, an aircrafttransparency, and a motor vehicle transparency.
 9. The article of claim1, wherein the substrate has a thickness in the range of 0.2 mm to 20mm.
 10. The article of claim 1, wherein the functional coating has anemissivity of 0.1 or less.
 11. The article of claim 1, wherein thebarrier coating increases the emissivity of the coating stack by atleast a factor of two with respect to the emissivity of the functionalcoating.
 12. The article of claim 1, wherein the barrier coatingincreases the emissivity of the coating stack by a factor in the rangeof 2 to 20 compared to the emissivity of the functional coating.
 13. Thearticle of claim 1, wherein the functional coating has an emissivity ofless than or equal to 0.1 and the coating stack has an emissivity ofgreater than or equal to 0.5.
 14. The article of claim 1, wherein theemissivity of the coating stack is 0.5 to 0.8.
 15. The article of claim1, wherein the barrier coating has a thickness of greater than or equalto 1 micron.
 16. The article of claim 1, wherein the barrier coating hasa thickness of less than or equal to 5 microns.
 17. The article of claim1, wherein the barrier coating comprises 0 wt. % to 100 wt. % aluminaand 100 wt. % to 0 wt. % silica.
 18. The article of claim 1, wherein thebarrier coating comprises at least 35 wt. % alumina.
 19. The article ofclaim 1, wherein the barrier coating comprises 50 wt. % to 75 wt. %alumina and 25 wt. % to 50 wt. % silica.
 20. The article of claim 1,wherein the barrier coating comprises 15 wt. % to 70 wt. % alumina and85 wt. % to 30 wt. % silica.
 21. The article of claim 1, wherein thebarrier coating comprises 75 wt. % to 85 wt. % alumina and 15 wt. % to25 wt. % silica.
 22. The article of claim 1, wherein the barrier coatingcomprises 86 wt. % to 90 wt. % alumina and 10 wt. % to 14 wt. % silica.23. The article of claim 1, wherein the barrier coating comprises 50 wt.% to 60 wt. % alumina and 40 wt. % to 50 wt. % silica.
 24. The articleof claim 1, wherein the barrier coating comprises 55 wt. % alumina and45 wt. % silica.
 25. The article of claim 1, wherein the barrier coatinghas a thickness in the range of 300 Å to 1,500 Å.
 26. The article ofclaim 23, wherein the barrier coating has a thickness in the range of500 Å to 1,000 Å.
 27. The article of claim 24, wherein the barriercoating has a thickness of 800 Å.
 28. The article of claim 1, whereinthe barrier coating comprises a first layer formed over the functionalcoating and a second layer formed over the first layer, wherein thefirst layer comprises 50 wt. % to 100 wt. % alumina and 50 wt. % to 0wt. % silica, and the second layer comprises 50 wt. % to 100 wt. %silica and 50 wt. % to 0 wt. % alumina.
 29. The article of claim 28,wherein the first layer comprises 70 wt. % to 100 wt. % alumina and 30wt. % to 0 wt. % silica.
 30. The article of claim 28, wherein the firstlayer comprises 100 wt. % alumina.
 31. The article of claim 28, whereinthe first layer comprises 50 wt. % to 60 wt. % alumina and 40 wt. % to50 wt. % silica.
 32. The article of claim 28, wherein the first layercomprises 55 wt. % alumina and 45 wt. % silica.
 33. The article of claim28, wherein the first layer has a thickness in the range of 50 Å to1,000 Å.
 34. The article of claim 30, wherein the first layer has athickness in the range of 50 Å to 200 Å.
 35. The article of claim 30,wherein the first layer has a thickness of 125 Å.
 36. The article ofclaim 31, wherein the first layer has a thickness in the range of 50 Åto 400 Å.
 37. The article of claim 32, wherein the first layer has athickness of 200 Å.
 38. The article of claim 28, wherein the secondlayer comprises 70 wt. % to 100 wt. % silica and 30 wt. % to 0 wt. %alumina.
 39. The article of claim 28, wherein the second layer comprises80 wt. % to 95 wt. % silica and 5 wt. % to 20 wt. % alumina.
 40. Thearticle of claim 28, wherein the second layer has a thickness in therange of 50 Å to 2,000 Å.
 41. The article of claim 39, wherein thesecond layer has a thickness in the range of 300 Å to 1,000 Å.
 42. Thearticle of claim 39, wherein the second layer has a thickness of 500 Å.43. The article of claim 1, wherein the barrier coating provides anoxygen permeability of less than or equal to 1.5 cubic cm of oxygen gasat a thickness of one mil for 100 square inches over a period oftwenty-four hours under an oxygen partial pressure differential of oneatmosphere at 23° C. and a relative humidity of zero.
 44. The article ofclaim 1, wherein the barrier coating is solar absorbing in at least oneof the UV, IR, or visible regions of the electromagnetic spectrum. 45.The article of claim 1, wherein the article is a monolithictransparency.
 46. A method of making a conditioned coated substrate,comprising: providing a substrate; forming at least one functionalcoating over at least a portion of the substrate; forming at least onebarrier coating over at least a portion of the functional coating todefine a coating stack, wherein the barrier coating is stable tooxygen-containing gases and limits the transmission of oxygen-containinggases to materials over which it is deposited; and conditioning thesubstrate by at least one conditioning process selected from heating,bending or tempering.
 47. The method of claim 46, including forming atleast one other oxygen barrier coating over at least a portion of thesubstrate and forming the at least one functional coating over the atleast one other barrier coating such that the at least one other barriercoating is positioned between the substrate and the functional coating.48. The method of claim 46, including forming the barrier coating to athickness in the range of greater than 100 Å to less than 10 microns.49. The method of claim 46, wherein the barrier coating has a refractiveindex in the range of 1.4 to 1.8.
 50. The method of claim 46, whereinthe functional coating has an emissivity of 0.1 or less.
 51. The methodof claim 46, wherein the barrier coating increases the emissivity of thecoating stack by at least a factor of two with respect to the emissivityof the functional coating.
 52. The method of claim 46, wherein thebarrier coating increases the emissivity of the coating stack by afactor in the range of 2 to 20 compared to the emissivity of thefunctional coating.
 53. The method of claim 46, wherein the functionalcoating has an emissivity of less than or equal to 0.1 and the coatingstack has an emissivity of greater than or equal to 0.5.
 54. The methodof claim 46, including forming the barrier coating to a thickness ofgreater than or equal to 1 micron.
 55. The method of claim 46, includingforming the barrier coating to a thickness of less than or equal to 5microns.
 56. The method of claim 46, wherein the barrier coatingcomprises 0 wt. % to 100 wt. % alumina and 100 wt. % to 0 wt. % silica.57. The method of claim 46, wherein the barrier coating comprises atleast 35 wt. % alumina.
 58. The method of claim 46, wherein the barriercoating comprises 50 wt. % to 75 wt. % alumina and 25 wt. % to 50 wt. %silica.
 59. The method of claim 46, wherein the barrier coatingcomprises 15 wt. % to 70 wt. % alumina and 85 wt. % to 30 wt. % silica.60. The method of claim 46, wherein the barrier coating comprises 75 wt.% to 85 wt. % alumina and 15 wt. % to 25 wt. % silica.
 61. The method ofclaim 46, wherein the barrier coating comprises a first layer formedover the functional coating and a second layer formed over the firstlayer, wherein the first layer comprises 50 wt. % to 100 wt. % aluminaand 50 wt. % to 0 wt. % silica, and the second layer comprises 50 wt. %to 100 wt. % silica and 50 wt. % to 0 wt. % alumina.
 62. The method ofclaim 61, wherein the first layer comprises 70 wt. % to 100 wt. %alumina and 30 wt. % to 0 wt. % silica.
 63. The method of claim 61,wherein the first layer has a thickness in the range of 50 Å to 1micron.
 64. The method of claim 61, wherein the first layer has athickness in the range of 100 Å to 250 Å.
 65. The method of claim 61,wherein the second layer comprises 70 wt. % to 100 wt. % silica and 30wt. % to 0 wt. % alumina.
 66. The method of claim 65, wherein the secondlayer has a thickness in the range of 50 Å to 2,000 Å.
 67. The method ofclaim 65, wherein the second layer has a thickness in the range of 300 Åto 500 Å.
 68. The method of claim 46, wherein the barrier coatingprovides an oxygen permeability of less than or equal to 1.5 cubic cm ofoxygen gas at a thickness of one mil for 100 square inches over a periodof twenty-four hours under an oxygen partial pressure differential ofone atmosphere at 23° C. and a relative humidity of zero.